A good carb should run for years without problems, once setup properly.
Pinging likes to happen under load and low rpm, as in right when you start getting in high gear and flooring the pedal on the bottom of a hill or incline.
You mentioned before you already got factory timing setting with help of a light.
After that you don't need a light any more, unless you are curious what the final setting looks like.
After you are done advancing, let's hope that solved your issues...
At least you learned something and eliminated one step in trouble-shooting and are one step closer to get it all right.
Never get frustrated. You gotta have fun working and especially fine tuning these trucks and engines.
Nothing like that feeling, when she runs like a dream with the help of your own hands.
